I have a pair of KRK KNS 8400's, I'm actually using them right now. Very nice. Comfortable, fairly flat eq for mixing and such, good for music too because they give a more "true" sound of whatever you are listening to

Those M50s aren't bad at all, but if you're willing to spend around 300 USD you can do better for sure...unless you meant
200 USD. I love me some Grados, but I'm not sure how you feel about open back headphones. Maybe the SR-225 or SR-
325? You could possibly swing a used pair of the Grado Reference Series if you're lucky. There was a time you could pick
up some Sennheiser HD-600 cans for $300. Possibly the AKG K550? Well, there are a few to get you thinking. It all
depends on your specific taste/needs.

yeah with a budget of $300, you might look into a few more options than the ath m50s. they're good if your budget is like $150/200, but you might be able to find something better for around $300. try headfi.org